| 摘要 |
PURPOSE:To make the stretching of the pores during press-forming uniform so as to improve the quality of the periphery of the fluorescent screen by making the pore diameter of the peripheral 6 rows of the shadow mask of the color picture tube 10-50% smaller than the pore diameter of the remaining part. CONSTITUTION:A shadow mask 1 in a color picture tube having a negative guard band, dot-type fluorescent surface is formed so that the shadow mask will have an effective pore part 2 and uneffective pore part 3. At the same time, the pore diameter of the pripheral 6 rows of the effective pore part 2 is made 10- 50% smaller than that of the remaining part. As the change rate of the equivalent plate thickness is reduced by half in the peripheral part which is the border between the effective pore part and the uneffective pore part 3, the stretching of the shadow mask during press-forming is made uniform and generation of defects during forming, such as deflection, can be avoided. Also, as the effect of the pore diameter of the fluorescent body on the fluorescent surface can be reduced, the quality of the fluorescent film and its purity can be improved. |
